To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition rating of 95 (EF+), indicating that it is in very good shape. This is relevant because coins in better condition tend to fetch higher prices at auctions.

2. Previous Auction Prices: Looking at previous auction prices for coins with a similar condition (95), we find:
- In 2018, a coin with a condition of 95 sold for 380 euros.
- In 2014, another coin with a condition of 95 sold for 470 euros.
- In 2021, a coin with a condition of 95 sold for 480 euros.

3. Starting Price and Average Auction Price: The current starting price is 300 euros, and the average auction price for this coin in the past is 201.96 euros. However, given that the current condition is high, it is reasonable to expect that the auction price will be above this average.

4. Auction Trends: The coin has been auctioned 57 times, with a high sales percentage (52 out of 57). This suggests that there is consistent interest in this coin, which may influence the price.

5. Maximum Price Estimation: Based on previous auction prices for coins of similar condition and considering the trend of increasing prices, a reasonable maximum purchase price could be in the range of 500 to 600 euros.

Therefore, an estimated maximum purchase price for this coin could be approximately 600 euros.